A drill bit equivalency chart converts metric sizes to fractional or decimal-inch equivalents. Drill bits can be made in any size but manufacturers use defined measurements and dimensions to create the bits stocked by most distributors.
Nearly all countries use metric dimensioning to define drill bit diameter and length. Conversion charts provide U.S. and British equivalency for metric drill bit sizes. Most metric drill-bit sets are sized in 1 millimeter increments, but specialty suppliers can provide bits that have less routine sizes and dimensions. Fractional inch drill-bit sets are commonly used throughout the United States. Conversion charts are also used to convert number and letter gauge drill-bit sizes into metric or fractional inch equivalents.